An IHttpModule for Enabling CORS

CrossOriginSupportModule.cs

using System;
using System.Web;

namespace SSSWorld.CorsHelper
{
    public class CrossOriginSupportModule : IHttpModule
    {
        public const string Options = "OPTIONS";
        public const string Origin = "Origin";
        public const string AccessControlRequestMethod = "Access-Control-Request-Method";
        public const string AccessControlRequestHeaders = "Access-Control-Request-Headers";

        public const string AccessControlAllowOrigin = "Access-Control-Allow-Origin";
        public const string AccessControlAllowMethods = "Access-Control-Allow-Methods";
        public const string AccessControlAllowHeaders = "Access-Control-Allow-Headers";
        public const string AccessControlAllowCredentials = "Access-Control-Allow-Credentials";
        public const string AccessControlMaxAage = "Access-Control-Max-Age";

        public void Init(HttpApplication context)
        {
            context.BeginRequest += ContextOnBeginRequest;
            context.PreSendRequestHeaders += ContextOnPreSendRequestHeaders;
        }

        private void ContextOnPreSendRequestHeaders(object sender, EventArgs eventArgs)
        {
            var application = (HttpApplication)sender;
            var context = application.Context;
            var response = context.Response;

            response.Headers[AccessControlAllowOrigin] = "*";
        }

        private void ContextOnBeginRequest(object sender, EventArgs eventArgs)
        {
            var application = (HttpApplication)sender;
            var context = application.Context;
            var request = context.Request;

            if (!String.IsNullOrEmpty(request.Headers[Origin]))
            {
                if (request.HttpMethod == Options)
                {
                    context.Response.Headers[CrossOriginSupportModule.AccessControlAllowMethods] = "GET,POST,PUT,OPTIONS,DELETE";
                    context.Response.Headers[CrossOriginSupportModule.AccessControlAllowHeaders] = "X-Requested-With, Authorization, X-Authorization, X-Authorization-Mode, User-Agent, Accept, Content-Type, If-Match, Cookie, X-Applicaton-Name, X-Application-Version";
                    context.Response.Headers[CrossOriginSupportModule.AccessControlMaxAage] = 1728000.ToString();
                    // interrupt request, so it does not get processed by SLX Authentication module
                    context.Response.End();
                }
            }
        }

        public void Dispose()
        {

        }
    }
}

Web.config

This module enables Cross Origin requests.

To use it, copy to the bin folder and add the following to web.config (make sure the add tag is at the top of the section):

<modules>
  <add name="CrossOriginSupportModule" type="SSSWorld.CorsHelper.CrossOriginSupportModule, SSSWorld.CorsHelper" />
</modules>